Fix download order in Gateway offline download playbook

[kvelarde-itential]

• Removed Python devel RPM from Gateway Python RPM list (it's already part of the Gateway build RPM list)
• FIxed issue with downloading RPMs using repotrack (it's not currently being used though)
• Removed archives directory from Gateway download since it's not used
• Moved the Gateway download tasks to separate files for better readability
• Reordered the Gateway downloads so that the Python RPMs are downloaded before the build packages.

Note that some Python RPMs will still be in the build directory since we are downloading the Python devel RPM.

Used Themis to test RHEL 8, RHEL 9, Rocky 8 and Rocky 9 Gateway offline installs.